Pitch recovery and its utilization in a cracking process



G. w. BRITTON 3,200,062

2 Sheets-Sheet 1 PITCH RECOVERY AND ITS UTILIZATION IN A CRACKING PROCESS mm Iota W mm R n 8 J we mm n 295 159 r, 233u G mm u do m o P #m\ H mm 6 mm mm M5310 8&8

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Filed April so, 1962 r p 821693 320 Eu] 9 m o 55 A TTORNEKS g- 10, 1955 G. w. BRITTON 3,200,062

PITCH RECOVERY AND ITS UTILIZATION IN A CRACKING PROCESS Filed April 50, 1962 r 2 Sheets-Sheet 2 BY %7 "6; q IO ATTORNEYS United States Patent 3,200,062 PITCH RECOVERY AND ITS UTILIZATION IN A CRACKING PROCESS Gene W. Britten, Phillips, Tex, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Apr. 30, 1962, Ser. No. 191,161 '7 iCiaims. (Cl. 208-87) This invention relates to the recovery of petroleum pitch. In one aspect, the invention relates to a process for the production of useful products from petroleum pitch by catalytic cracking. In another aspect, the invention relates to a process for melting, dissolving and feeding petroleum pitch to a catalytic cracking reactor. In another aspect, the invention relates to means for melting, dissolving and feeding petroleum pitch to a catalytic cracking reactor.

Large demand for motor fuels has resulted in the recovery of maximum amounts of these components from petroleum crude oil. One Way to recover maximum amounts of the desired products is by vacuum distillation, for example, as disclosed and claimed in US. 2,901,426, Waddill et al., 1959. Maximum recovery of motor fuels by vacuum distillation results in a residuum of solid pitch, and effective and economic utilization of this pitch has been a very desirable objective.

An object of my invention is to produce useful hydrocarbon products from pitch resulting from vacuum distillation of crude petroleum.

Another object of my invention is to provide means for feeding a petroleum pitch to a catalytic cracking reactor.

A further object of my invention is to feed a difiicultly soluble petroleum pitch to a catalytic cracking step.

Another object of this invention is to prepare 21 petroleum pitch for feeding to a catalytic cracking step by feeding and dissolving with a solvent.

Another object of my invention is to provide means for heating and dissolving petroleum pitch and feeding to a catalytic cracking reactor.

Other aspects, objects and the advantages of my invention are apparent in the written description, the drawing and the claims.

According to may invention, petroleum pitch is reclaimed and cracked by dissolving the pitch in an aromatic extract oil obtained from the cracking step and charging the resulting solution to a mobile catalyst topped crude cracking zone along with topped crude. The topped crude has an A.P.I. gravity, 60 F./60 F., in the range of 15 to 26. The pitch is a residuum from vacuum reduction of West Texas topped crude having a specific gravity,

60 F./60 F., in the range of 1.002 to 1.135, a penetration, seconds, 100 gm., 77 F., in the range of 0-10, and a ring and ball softening point in the range of 180 to 260 F. The aromatic extract oil is obtained by solvent extraction of a cycle oil obtained from the same cracking step to which the pitch is fed and has the following characteristics: A.P.I. gravity, 60 F./60 F., in the range of 7.1 to 20; B.M.C.I. in the range of 60 to 99; and 50% point, F., in the range of 550 to 725. Preferably, the solvent is an extract oil resulting from S0 extraction of light cycle oil, heavy cycle oil or decant oil, or a combination of these oils, and having an A.P.I. gravity, 60 F160 F., in the range of 8.5 to 15; B.M.C.I. in the range of 78 to 99; and 50% point, F., in the range of 630 to 680. The extract oil and pitch are blended in a ratio in the range of 5 volumes of extract oil to 1 volume of pitch to equal volumes of extract oil and pitch, that is, in the range of 5:1 to 1:1. in extract oil is charged to a topped crude catalytic cracking step in which the volume of topped crude is in the The solution of pitch range of 10 to 50 times the volume of the total pitch charged; that is, the volume ratio of topped crude to the pitch-extract oil solution is in the range of 50:1 to 10:1.

Further, according to my invention, petroleum pitch is reclaimed and cracked by heating and dissolving the pitch in a melt zone in contact with steam and a solvent for the pitch while stirring, transferring the melted and dissolvel pitch to a blend tank, further heating the mixture in the blend tank while stirring, and continuously recycling part of the blend back to the belt tank While continuously charging the remainder to a topped crude catalytic cracking zone. The ranges of solvent to pitch and solventpitch mixture to topped crude, the characteristics of the pitch and solvent are all as indicated above. The temperature in the melt tank is preferably maintained at least 10 F. above the softening point of the pitch, preferably in the range of 200 to 350 F. The upper temperature in both the melt tank and the blend tank is a function of the initial boiling point of the solvent, being maintained low enough to prevent a substantial amount of vaporization of the solvent. The temperature in the blend tank is maintained in the range of 250 to 400 F., preferably between 20 and F. above the temperature in the melt tank. The volume ratio of the portion recycled to the melt tank to the portion fed to catalytic cracking is in the range of 2:1 to 1021.

Further according to my invention, there are provided means for reclaiming and cracking petroleum pitch, comprising a melt tank, means to feed solid pitch to the melt tank, means to supply a pitch solvent and heat to the melt tank and to stir the contents of the tank, a blend tank, means to transfer melted and dissolved pitch from the melt tank to the blend tank to maintain a liquid level in the melt tank, means to supply heat to the blend tank and to stir the contents thereof, and means to recirculate the blend from the blend tank to the melt tank and to feed a portion to the topped crude catalytic reactor. Preferably, the means to supply a pitch solvent comprise distillation means to separate the effluent from the catalytic reactor and recover a relatively high aromatic fraction and solvent extraction means to separate the fraction and recover a solvent having a B.M.C.I. aromaticity in the range of 78 to 99.

In the drawing, FIGURE 1 is a block diagram illustrating the steps of my invention.

FIGURE 2 is a schematic illustration of apparatus for preparing and feeding pitch to a catalytic cracking reactor.

In the system illustrated in FIGURE 1, topped crude is charged to a catalytic cracking zone 11 through an inlet line 12. The etliuent from cracker 11 is fed through pipe 13 into a fractional distillation and slurry settling zone 14. In zone 14- the efliuent stream is divided into a light gas fraction Withdrawn through pipe 16, a gasoline fraction Withdrawn through pipe 17, a light cycle oil removed through pipe 18, a heavy cycle oil withdrawn through pipe 19, a decant oil removed through pipe 21, and a slurry comprising heavy hydrocarbons and catalyst which is recycled to cracking zone 11 through pipe 22. Connections are provided whereby light cycle oil, heavy cycle oil and decant oil can be Withdrawn from the system through pipes 23, 24 and 25, respectively, or can be transferred to solvent extraction zone 27 through connections with pipe 28, or can be used directly as a solvent for the pitch by transfer through line 29. In solvent extraction zone 27, a separation is made according to the structure of the hydrocarbons whereby the more aromatic fraction is removed through pipe 31 for use as a pitch solvent in pitch heating and dissolving zone 32, or removed through pipe 33 as an aromatic product.

The pitch which is removed from the pits and transferred mechanically to zone 32 is therein heated, stirred removed through pipe 71 as an aromatic product.

and dissolved with the solvent and fed through pipe 34 into inlet line 12, along with topped crude, and fed to catalytic cracking zone 11. The portion of FIGURE 1 within the dashed rectangle in the lower left portion of the figure represents two embodiments of my invention. In one embodiment, vacuum distillation zone 36 is used to separate a West Texas topped crude into a residual pitch and a heavy virgin gas oil, the pitch being transferred through pipe 37 to pitch storage at 38, as for example an open pit. In this embodiment, the topped crude which passes to vacuum distillation zone 36 can be from a separate source from the topped crude winch is fed to catalytic cracking zone 11 or can be from the same source but processed at a different time. Vacuum distillation zone 36 represents vacuum distillation as described, for example, in the above-referred to US. 2,901,426 and preferably is operated in a plurality of stages, preferably three.

To prevent large accumulations of pitch, my invention can be operated by processing and feeding the pitch to catalytic cracking zone 11 simultaneously with its formation in vacuum distillation zone 36. An advantage of an operation in which the topped crude is charged continuously to the cracking zone and to the vacuum distillation zone is that a maximum amount of material which can be charged to a clean oil cracking unit is produced, including the material removed from the topped crude in the vacuum distillation zone as well as that removed in the topping step, while at the same time preventing a build-up of pitch since it can be charged along with the topped crude to the so-called dirty oil cracking step. The combination of clean oil and dirty oil units is described in more detail in copending application Serial No. 84,263, Slover et al., filed January 23, 1961, now abandoned.

To illustrate suitable pitch heating and dissolving means, together with a schematic representation of cracking, distillation, and solvent extraction steps, melt tank 41 is connected with blend tank 42 by an overflow line 43 which limits the height to which the mix in tank 41 can accumulate, as long as the level in tank 42 is lower than the outlet point of line 43 in tank 41. A recycle line 44 provides for return of blended mix from tank 42 into tank 41 through pump 46. Means for heating the mix in melt tank 41 are provided, represented by steam inlet and diffusion ring 47. Stirring means are provided by propeller 48 driven by motor 49. Feed tank 42 is provided with a similar stirring propeller 51 and motor 52 and with a heater 53 which comprises a gas inlet 54 and a stack 55. Tank 42 is connected by means of a pipe 56 and pump 57 with inlet 58 of a catalytic cracking reactor 59. Eflluent from reactor 59 passes to a fractional distillation column 61 through pipe 62 while a catalyst slurry is returned through pipe 63. Although a number of cuts can be made in column 61, only three are shown for simplicity in this figure, an overhead withdrawal 64, a bottoms draw 66 and an intermediate outlet 67, representing in this instance heavy cycle oil. This stream is passed to a solvent extraction column 68 where a separation is made between a high aromatic stream which passes through conduit 69 for use as a solvent for the pitch in tank 41, and in some instances a portion The remaining raffinate portion is removed through pipe 72. A ramp 73 is provided whereby dump trucks loaded with pitch can be driven and positioned to dump their loads of pitch through pitch inlet 74 into tank 41. Sufiicient heat is added in tank 41 to maintain the contents in a molten state although, as long as pitch is being added, there will be unmelted portions. Solvent is added continuously from pipe 69 and stirrer 48 keeps the contents well mixed. The material is permitted to overflow through pipe 43 into blend tank 42. Since the only comimunication permitting flow from tank 41 to tank 42 is a fluid conduit, at the opposite side of the tank from the pitch inlet, unmelted or undissolved pitch cannot reach tank 42 and thereforecannot be charged to the catalytic cracking zone. The material is heated further in tank 42 by heater 53 and a sizable portion is continuously recycled through tank 41 to maintain a suflicient quantity of well-blended material to assist in the mixing and melting of the pitch as added. The mixture to be fed to catalytic cracking zone 59 passes through pipe 56 and pump 57 and enters pipe 58 along with catalyst from pipe 75 from a catalyst regenerator (not shown). The contents of tank 42 are continuously stirred by propeller 51.

Example 7 In an example, according to my invention, 19,500 barrels per day of a topped crude of a West Texas crude oil, having an A.P.I. gravity at 60 F./60 F. of 23.6, is fed to cracking zone 11 along with 500 barrels per day of a pitch having a specific gravity at 60 F./60 F. of 1.129, a penetration, 5 seconds, gm., 77 F., of 2 and a ring and ball softeningpoint of 200 F. dissolved in 750 barrels per day of an extract oil obtained by S0 liquid extraction of the heavy cycle oil from pipe 14. The blend of pitch and extract oil fed through pipe 34 amounts to 1250 barrels per day and has an A.P.I. gravity at 60 F./60 F. of 3.8. From distillation zone 14, light gases, including olefinic and paraffinic C hydrocarbons and lighter, are removed at the rate of 31,400 pounds per hour, cracked gasoline is removed from line 17 at the rate of 4,700 barrels per day, light cycle oil is removed from pipe 24 at the rate of 3,350 barrels per day. Heavy cycle oil at the rate of 9,050 barrels per day is passed through pipe 19; 3,050 barrels per day of the heavy cycle oil is removed through pipe 24 and the remainder charged through pipe 28 to solvent extraction zone 27, yielding 4,200 barrels per day of raffinate and 2,550 barrels per day of aromatic extract, 1800 barrels per day being removed through pipe 21 and the remainder used forsolvent in zone 32. The catalytic reaction zone 11 is operated with a silica-alumina cracking catalyst in fluidized operation with a catalyst-to-feed weight ratio of 9: 1, at 890 F., at a pressure of 10 p.s.i.g. and produces about 30 percent conversion.

It'will be recognized by those skilled in the art that the drawings are schematic and that many necessary but common items of equipment, such as valves, pumps, controls, etc., are not shown. Such items of equipment can readily be supplied where needed for commercial operation.

Reasonable variation and modification are possible within the scope of my invention which sets forth method and apparatus for reclaiming and cracking petroleum pitch.

I claim:

1. A process for reclaiming and cracking petroleum pitch, which comprises: i

dissolving a pitch obtained by a vacuum distillation of a West Texas topped crude, said pitch having the following properties- Specific gravity, 60 F./60 F., in the range of Penetration, 5 sec., 100 gm., 77 F., in the range 5 2. A process for reclaiming and cracking petroleum pitch which comprises:

dissolving a pitch obtained by vacuum distillation of a West Texas topped crude, said pitch having the following properties- Specific gravity, 60 F./60 F., in the range of 1.002 to 1.135 Penetration, 5 sec., 100 gm., 77 F., in the range of -10 Softening point, ring and ball, F., in the range of 180-260 in an aromatic extract oil obtained by solvent extraction of an oil obtained from said catalytic cracking, said ex tract oil having the following characteristics A.P.I. gravity, 60 F./60 F., in the range of 7.1 to 20 B.M.C.I. in the range of 60 to 99 50% Point, F., in the range of 550 to 725, the volume ratio of said extract oil to said pitch being in the range of :1 to 1:1; and charging the resulting solution to a fluidized catalyst topped crude cracking step, the volume ratio of the topped crude to the charge of pitch and extract oil being in the range of 50:1 to :1.

3. A process for reclaiming and cracking petroleum pitch, which comprises:

charging said pitch to a melt zone; heating and dissolving said pitch in said melt zone by contact with steam and a solvent for said pitch while stirring; I transferring said melted and dissolved pitch to a blend zone; further heating said melted and dissolved pitch in said blend zone, while stirring; continuously transferring a first portion of further heated melted and dissolved pitch from said blend zone to said melt zone; and continuously charging a second portion of further heated, melted and dissolved pitch to a topped crude catalytic cracking step. 4. A process for reclaiming and cracking petroleum pitch, which comprises:

charging to a melt zone said pitch having the following properties- Specific gravity, 60 F./60 F., in the range of 1.002 to 1.135 Penetration, 5 sec., 100 gm., 77 F., in the range of 0-10 Softening point, ring and ball, F, in the range of 180-260; heating and dissolving said pitch in said melt zone by contact with steam and a solvent for said pitch while stirring, said solvent being an aromatic extract oil obtained by solvent extraction of an oil obtained from said cracking and having the following characteristics- A.P.l. gravity, 60 F./60 F., in the range of 7.1 to B.M.C.I. in the range of 60 to 99 50% Point, F., in the range of 550 to 725, the volume ratio of said extract oil charged to said pitch charged being in the range of 5:1 to 1: 1;

transferring said melted and dissolved pitch to a blend zone; further heating said melted and dissolved pitch in said blend zone while stirring; continuously transferring a first portion of further heated, melted and dissolved pitch from said blend zone to said melt zone; and continuously charging a second portion of further heated, melted and dissolved pitch to a topped crude catalytic cracking step, the volume ratio of the topped crude to said pitch charged to said catalytic cracking step being in the range of 50:1 to 10:1. 5. A process for reclaiming and cracking petroleum pitch, which comprises:

6 charging to a melt zone a pitch having the following properties- Specific gravity, 60 F./60 F., in the range of 1.002 to 1.135 Penetration, 5 sec., grre, 77 F., in the range of 0-10 Softening point, ring and ball, F., in the range of -260; heating and dissolving said pitch While stirring in said melt zone by contact with steam and a solvent comprising an aromatic extract oil obtained by S0 extraction of a heavy cycle oil obtained from said cracking, said extract oil having the following characteristics A.P.I. gravity, 60 F./60 F., in the range of 8.5 to 15 B.M.C.I. in the range of 78 to 99 50% point, F., in the range of 630 to 680, the volume ratio of said extract oil to said pitch being in the range of 5:1 to 1:1;

maintaining in said melt zone a temperature in the range of 200 to 350 F., transferring said melted and dissolved pitch to a blend zone; further heating said melted and dissolved pitch in said blend zone while stirring; maintaining in said blend zone a temperature in the range of 250 to 400 F.; continuously transferring a first portion of further heated, melted and dissolved pitch from said blend zone to said melt zone; continuously charging a second portion of further heated, melted and dissolved pitch to a topped crude catalytic cracking zone, the volume ratio of said portion transferred to said melt zone and said portion charged to said catalytic cracking zone being in the range of 2:1 to 10:1 and the volume ratio of topped crude to said second portion charged to said catalytic cracking zone being in the range of 50:1 to 10:1. 6. A process for reclaiming and cracking petroleum pitch, which comprises:

dissolving a pitch obtained by a vacuum distillation of a West Texas topped crude, said pitch having the following properties- Specific gravity, 60 F./60 F., in the range of 1.002 to 1.135 Penetration, 5 sec., 100 gm., 77 R, in the range of 0-10 Softening point, ring and ball, F. in the range of 180-260 in an aromatic extract oil obtained by S0 extraction of a heavy cycle oil obtained from said catalytic cracking, said extract oil having the following characteristics- A.P.I. gravity 60 F./60 F. in the range of 8.5 to 15 B.M.C.I. in the range of 78 to 99 50% point, F. in the range of 630 to 680; and charging the resulting solution to a mobile catalyst topped crude cracking step.

7. A process for treating topped crude which comprises:

passing a first portion of said topped crude into a catalytic cracking zone; passing a second portion of said topped crude into a vacuum distillation zone; in said vacuum distillation zone producing a heavy virgin gas oil and a petroleum pitch having the following properties- Specific gravity, 60 F./60 F. in the range of 1.002 to 1.135 Penetration 5 sec. 100 gm., 77 F. in the range of 0-10 Softening point, ring and ball F. in the range of 180-260 dissolving said pitch in an aromatic extract oil obtained by solvent extraction of an oil obtained from said catcharacteristics A.P.I. gravity 60 F./ 60 F. in the range of 7 .1 to 20 B.M.C.I. in the range of 60 to 99 50% point, F. in the range of 550 to 7 25 K the volume ratio of said extract oil to said pitch being in the range'of 5:1 to 1:1; and' charging the resulting solution to a fluidized catalyst topped crude cracking step, the volume ratio of the 8' References Cited by the Examiner UNITED STATES PATENTS 2,133,240 10/38 Atwell 208- 86 2,882,218 4/59 Jewell 208-157 2,904,504 9/59 Rice 7 t 208 -164 2,937,135 3/60 Middleton 20887 ALPHONSO D. SULLIVAN,VPrimary Examiner.

topped crude to the charge of pitch and extract oil being 10 ABRAHAM RIMENS, Examiner.

in the range of 50:1 to 10:1. 

1. A PROCESS FOR RECLAIMING AND CRACKING PETROLEUM PITCH, WHICH COMPRISES: DISSOLVING A PITCH OBTAINED BY A VACUUM DISTILLATION OF A WEST TEXAS TOPPED CRUDE, SAID PITCH HAVING THE FOLLOWING PROPERTIESSPECIFIC GRAVITY, 60*F./60*F., IN THE RANGE OF 1.002 TO 1.135 PENETRATION, 5 SEC., 100 GM., 77*F., IN THE RANGE OF 0-10 SOFTENING POINT, RING AND BALL, *F., IN THE RANGE 180-260 IN AN AROMATIC EXTRACT OIL OBTAINED BY SOLVENT EXTRACTION OF AN OIL OBTAINED FROM SAID CATALYTIC CRACKING, SAID EXTRACT OIL HAVING THE FOLLOWING CHARACTERISTICSA.P.I. GRAVITY, 60*F./60*F., IN THE RANGE OF 7.1 TO 20 B.M.C.I. IN THE RANGE OF 60 TO 99 50% POINT, *F., IN THE RANGE OF 550 TO 725; AND CHARGING THE RESULTING SOLUTION TO A MOBILE CATALYST TOPPED CRUDE CRACKING STEP. 